Within practical limits, yes. Mirror is cut to order from stock sheets, so almost any rectangle and most shapes can be produced. The ceilings are the size of the sheet, the weight a wall and a pair of installers can handle, and whether the finished piece can physically get into the room. Long walls are covered in multiple panels.
Three things cap a single piece. The first is the stock sheet itself. The second is weight, since glass gets heavy quickly and a tall wide mirror becomes a careful two or three person carry that also has to be held flat, because a big panel flexed the wrong way while it is being lifted will crack. The third is the path: the doorway, the turn at the bottom of the stairs, the elevator, the tight corner into the powder room.
When a wall is longer than any of that allows, it goes in as multiple panels with tight butt seams. Cut from the same run so the tone matches end to end, and with the joints laid out where the eye expects them, a paneled wall reads as one surface from a step back.
Arches, radius corners, full circles, angled cuts to follow a stair, notches around sconce boxes, cutouts for a faucet coming through a backsplash, and drilled holes for standoffs or rosettes are all ordinary work. What they need is a template rather than a tape measure, taken in the room, because a shape that is off by a small amount in the shop is off by a visible amount on the wall.
One order of operations matters here. Every cut, notch and hole happens while the glass is still raw. Anything that will be tempered or given a safety backing is finished to final shape first, since neither one can be trimmed afterward.
A freshly cut edge is raw and sharp, so the edge treatment is part of the order, not an extra. A seamed edge takes the danger off and disappears behind a frame. A flat or pencil polished edge is what makes a frameless mirror look finished. A bevel puts a visible border of its own on the glass and changes how light plays at the perimeter. A properly worked and sealed edge also slows moisture from reaching the silver, which is where mirrors usually begin to fail.
Sometimes. Plain untempered mirror can be trimmed, though the new edge has to be worked afterward, and any polish or bevel on the side you remove is gone for good. Age is the risk, since old mirror with softening backing can chip or flake at the cut line. Anything tempered or safety backed cannot be cut at all.
The wall gets divided. Panel sizes are chosen so every piece clears the tightest turn on the way in, and the seams are placed deliberately, centered on the wall or lined up with a fixture rather than landing wherever the math fell. Panels cut from the same run match each other across the joints.
The Lodi showroom on Industrial Road takes walk ins Monday through Friday, nine to five, and Saturday nine to four. Bring a width, a height and a phone photo of the wall. Anything shaped, notched or oversized gets templated at the house instead of guessed at the counter.